1. Field of the Invention
The present invention relates to a character display apparatus and a character display method capable of displaying a character with a high definition using a color display device, and a recording medium for use with such apparatus and method.
2. Description of the Related Art
For example, a conventional technique for displaying a character on a display apparatus uses a dot font which is based on two binary values corresponding to black and white. In this conventional technique, the outline and inside of each character stroke is displayed in black and the remaining space is displayed in white.
As an improvement to the conventional dot font-based technique, another conventional technique (e.g., Japanese Laid-Open Publication No. 8-255254) uses a gray-scale font. In this conventional technique, a gray-scale area is provided around each black area.
FIG. 1 illustrates an outline of an ideal oblique line 102 which can be output on an output plane 100 by using an output device with a very high resolution. Such an oblique line may be used as a part of a character.
FIG. 2 illustrates the oblique line 102 of FIG. 1 being displayed on a 6xc3x9712-pixel display plane 200 using the conventional dot font. Referring to FIG. 2, each hatched box represents a pixel displayed in black and each open box represents a pixel displayed in white.
In FIG. 2, the oblique line 102 of FIG. 1 is displayed as a combination of four line segments, resulting in a substantial degree of jaggedness. Therefore, the shape (a part of a character) illustrated in FIG. 2 cannot be viewed by a human eye as a smooth oblique line. Thus, a character displayed with the conventional dot font cannot be seen by a human eye as a well-defined character because jaggedness occurs along oblique lines or curves of the character. Particularly, when a character is displayed with a small number of dots, a greater degree of jaggedness is observed.
FIG. 3 illustrates the oblique line 102 of FIG. 1 being displayed on a 6xc3x9712-pixel display plane 300 using the conventional gray-scale font. Referring to FIG. 3, each level 3 box represents a pixel displayed in black, each level 2 box represents a pixel displayed in dark gray, each level 1 box represents a pixel displayed in light gray, and each level 0 box represents a pixel displayed in white.
Where each color element is controlled with, for example, 256 gray-scale levels, a black corresponding to level 3 is displayed by setting the brightness (R, G, B) of a color element (corresponding to one pixel of a color liquid crystal display apparatus) to (0, 0, 0). Similarly, dark gray corresponding to level 2 is expressed by (R, G, B)=(80, 80, 80), light gray corresponding to level 1 is expressed by (R, G, B)=(160, 160, 160), and white corresponding to level 0 is expressed by (R, G, B)=(255, 255, 255).
The shape (a part of a character) of FIG. 3 appears to have been improved in terms of jaggedness from that of FIG. 2. This is because a gray correction is performed on a dot by dot basis. However, the conventional technique using the gray-scale font has the following problems: the dot-by-dot correction is limited with a low resolution; and the outline of the character or the character itself may be blurred, or the blackness of the character may be non-uniform, because a gray color is used in and around a part of the outline of the character.
According to one aspect of this invention, a character display apparatus includes: a display device having a plurality of pixels; and a control section for controlling the display device. Each of the pixels includes a plurality of sub-pixels arranged along a predetermined direction. A corresponding one of a plurality of color elements is pre-assigned to each of the sub-pixels. The control section displays a character on the display device by independently controlling the color elements respectively corresponding to the sub-pixels.
In one embodiment of the invention, an intensity of each of the color elements is represented stepwise through a plurality of color element levels. Each of the sub-pixels has one of the color element levels. The control section sets a color element level of at least one particular sub-pixel corresponding to a basic portion of a character to be displayed on the display device to a predetermined color element level, and sets a color element level of at least one other sub-pixel adjacent to the at least one particular sub-pixel corresponding to the basic portion of the character to a color element level other than the predetermined color element level.
In one embodiment of the invention, the control section defines the basic portion of the character to be displayed on the display device based on an outline of a scaled character.
In one embodiment of the invention, the control section defines the basic portion of the character to be displayed on the display device based on skeleton data which represents a skeleton shape of the character.
In one embodiment of the invention, the control section scales the skeleton data according to a size of the character to be displayed on the display device, an d adjusts a line width of the character after defining the basic portion of the character based on the scaled skeleton data.
In one embodiment of the invention, the control section sets the color element level of the at least one other sub-pixel adjacent to the at least one particular sub-pixel corresponding to the basic portion of the character to the color element level other than the predetermined color element level based on at least one correction pattern.
In one embodiment of the invention, the control section adjusts a line width of the character to be displayed on the display device by selectively using one of the at least one correction pattern.
In one embodiment of the invention, the at least one correction pattern is provided in advance according to a size of the character to be displayed on the display device.
In one embodiment of the invention, the at least one correction pattern is provided in advance so as to correspond to the skeleton data.
In one embodiment of the invention, the at least one correction pattern is provided for each Chinese character radical.
In one embodiment of the invention, the at least one correction pattern is provided in advance according to the number of strokes of the skeleton data.
In one embodiment of the invention, the at least one correction pattern is provided in advance according to an inclination angle of a stroke of the skeleton data.
In one embodiment of the invention, the at least one correction pattern is provided in advance according to a distance between two portions of the basic portion of the character.
In one embodiment of the invention, where an arrangement of the at least one particular sub-pixel corresponding to the basic portion of the character forms a particular pattern, the control section corrects the color element level of the at least one particular sub-pixel corresponding to the basic portion of the character so as to divide the basic portion of the character into at least two portions.
In one embodiment of the invention, the skeleton data includes stroke information associated with each stroke. The control section sets the color element level of the at least one sub-pixel to the color element level other than the predetermined color element level according to a shape of the stroke.
In one embodiment of the invention, the skeleton data includes stroke information associated with each stroke. The control section sets the color element level of the at least one sub-pixel to the color element level other than the predetermined color element level based on a typeface attribute table which defines a feature of the typeface of the character in association with the stroke information.
In one embodiment of the invention, a plurality of typeface attribute tables are provided which define the feature of the typeface of the character in association with the stroke information. The control section sets the color element level of the at least one sub-pixel to the color element level other than the predetermined color element level based on one of the typeface attribute tables which is selectively used according to a size of the character.
In one embodiment of the invention, the control section sets a color element level of at least one sub-pixel adjacent in the predetermined direction to the at least one particular sub-pixel corresponding to the basic portion of the character to a color element level other than the predetermined color element level.
In one embodiment of the invention, the control section sets a color element level of at least one sub-pixel adjacent in a direction perpendicular to the predetermined direction to the at least one particular sub-pixel corresponding to the basic portion of the character to a color element level other than the predetermined color element level.
In one embodiment of the invention, the control section adjusts a line width of the character to be displayed on the display device by controlling the number of sub-pixels corresponding to the basic portion of the character.
In one embodiment of the invention, the control section adjusts a line width of the character to be displayed on the display device by controlling a color element level of a sub-pixel adjacent to the at least one particular sub-pixel corresponding to the basic portion of the character.
In one embodiment of the invention, the control section renders a feature of a typeface of the character to be displayed on the display device by controlling a color element level of a sub-pixel adjacent to the at least one particular sub-pixel corresponding to the basic portion of the character.
In one embodiment of the invention, the control section sets the color element level of one or more of the at least one particular sub-pixel corresponding to the basic portion of the character to be displayed on the display device to a color element level other than the maximum color element level.
In one embodiment of the invention, the control section sets the color element level of the at least one particular sub-pixel corresponding to the basic portion of the character based on a basic portion table.
In one embodiment of the invention, the control section sets the color element level of the at least one sub-pixel arranged in the vicinity of the at least one particular sub-pixel based on predetermined color element level information which is used to determine the color element level of the at least one sub-pixel arranged in the vicinity of the at least one particular sub-pixel corresponding to the basic portion of the character to be displayed on the display device.
In one embodiment of the invention, the character to be displayed on the display device has a color that is an achromatic color.
In one embodiment of the invention, the control section variably adjusts an interval between characters by performing a sub-pixel by sub-pixel control on a position of the character to be displayed on the display device.
In one embodiment of the invention, the control section converts the color element level of the sub-pixel to a brightness level based on a predetermined brightness table which defines a relationship between the color element level of the sub-pixel and the brightness level of the sub-pixel.
In one embodiment of the invention, the brightness table is prepared so as to be suitable for a display characteristic of the display device.
In one embodiment of the invention, the control section displays a character while rotating the sub-pixel arrangement by 90 degrees.
In one embodiment of the invention, the display device is a liquid crystal display device.
In one embodiment of the invention, the liquid crystal display device is a stripe-type liquid crystal display device.
According to another aspect of this invention, a character display method for displaying a character on a display device having a plurality of pixels is provided. Each of the pixels includes a plurality of sub-pixels arranged along a predetermined direction. A corresponding one of a plurality of color elements is pre-assigned to each of the sub-pixels. The method includes the step of displaying a character on the display device by independently controlling the color elements respectively corresponding to the sub-pixels.
According to still another aspect of this invention, a recording medium which can be read by an information display apparatus is provided. The apparatus includes a display device having a plurality of pixels and a controlling section for controlling the display device. Each of the pixels includes a plurality of sub-pixels arranged along a predetermined direction. A corresponding one of a plurality of color elements is pre-assigned to each of the sub-pixels. The recording medium has recorded thereon a program for instructing the control section to perform an operation of displaying a character on the display device by independently controlling the color elements respectively corresponding to the sub-pixels.
The function of the present invention will now be described.
According to the present invention, a plurality of color elements respectively corresponding to a plurality of sub-pixels are independently controlled. Therefore, it is possible to perform a sub-pixel by sub-pixel control which is finer than the conventional pixel by pixel control. Moreover, by appropriately controlling the color element of a sub-pixel in the vicinity of a sub-pixel corresponding to the basic portion of the character, colors of the character other than black can be made less conspicuous to a human eye. As a result, not only the outline of the character but also the character itself can be displayed with a high definition on a display device.
Moreover, according to the present invention, the basic portion of a character is defined based on skeleton data which represents the skeleton shape of a character. The color element level of a sub-pixel corresponding to the basic portion of the character is set to a predetermined color element level. Based on at least one correction pattern (or xe2x80x9ctransition patternxe2x80x9d), the color element level of a sub-pixel adjacent to the sub-pixel corresponding to the basic portion of the character is set to a color element level other than the predetermined color element level. By independently controlling the color element levels of sub-pixels in this manner, it is possible to perform a sub-pixel by sub-pixel control which is finer than the conventional pixel by pixel control. As a result, it is possible to virtually increase the resolution of a character. Moreover, by appropriately controlling the color element level of a sub-pixel adjacent to a sub-pixel corresponding to the basic portion of the character, colors of the character other than black can be made less conspicuous to a human eye. As a result, not only the outline of the character but also the character itself can be displayed with a high definition on a display device.
Furthermore, according to the present invention, the color element level of at least one particular sub-pixel corresponding to the basic portion of a character to be displayed on the display device is set to a predetermined color element level, while at least one of sub-pixels which is adjacent to the particular sub-pixel in a direction perpendicular to the sub-pixel arrangement direction is set to have a color element level other than the predetermined color element level. By independently controlling the color element levels of sub-pixels in this manner, it is possible to perform a sub-pixel by sub-pixel control which is finer than the conventional pixel by pixel control. As a result, it is possible to virtually increase the resolution of a character. Moreover, by appropriately controlling the color element level of a sub-pixel adjacent to a sub-pixel corresponding to the basic portion of the character, colors of the character other than black can be made less conspicuous to a human eye. As a result, not only the outline of the character but also the character itself can be displayed with a high definition on a display device.
Thus, the invention described herein makes possible the advantages of: (1) providing a character display apparatus capable of displaying a character with a high definition using a color display device; (2) providing a character display method capable of displaying a character with a high definition using a color display device; and (3) a recording medium for use with such apparatus and method.